Thread: Can I synchronize two master DB clusters except BDR ?

Hello,

While looking for a master/master replication solution i found this
solution https://www.symmetricds.org/ but never tested it, if you do
i'm interested in a feedback.
I ended up using master/slave with automatic failover (with repmgr).

Cordialement,
Nicolas KAROLAK | SysAdmin
6-8, rue André Voguet - 94200 Ivry-sur-Seine
+33 1 77 56 77 96 | www.ubicast.eu | www.ubicast.tv


2018-05-10 15:37 GMT+02:00 JaeWon Lee <thejaewon@gmail.com>:
> Hi ^^
> I want to synchronize two master DB clusters. (Each generates its own DML
> statements)
> I'm using postgresql-10 server.
> I know BDR can synchronize two master DB clusters.
> But current BDR2 cannot synchronize postgresql-10 servers.
> As I know, upcoming BDR3 can synchronize postgresql-10 servers but I cannot
> afford to pay for it. ( $9,000 per server and I'm startup. )
> I'm considering two methods.
>
> (1) Retain postgresql-10 server and find some method  to synchronize two
> master DB clusters.
>  - I know logical replication cannot deal with my problem. ( it's one
> direction only )
>  - Is there other method to use ?
>
> (2) Downgrade my DB server to 9.4 and use BDR1 for synchronizing.
>  - As I know, I can use BDR1 for free now.
>  - I'm using basic functions of postgresql-10 so I think downgrading itself
> may not cause big  problem. But I'm worrying about unknown problem.
>  - Are 9.4 and 10 different significantly?
>  - Can I upgrade my 9.4 data to 10 later ? This is what I really worry
> about.
>
> Could you give me any idea ?
>

Hi,

I have had a short time to play around with SymmetricDS and it is pretty easy to setup. There are two ways of doing it,
(1)two node setup:  master-slave (2) three node setup: centralized master sending and receiving updates to/from two
childnodes as the little diagram shows in the "Demo" section of the tutorials.
 

I've had to basically follow the manuals to configure both the setups and is very easy to start cracking with. It is
triggerbased just like Slony is, however, I could not test SymmetricDS with massive amounts of data as I 've tested
Slony.

Slony is robust but a little cumbersome to implement but if you know what you doing with Slony and follow the manuals,
itreally creates wonders. I have seen situations where Slony deamons were killed and restarted and it picked up from
whereit had left without breaking down completely.
 

Best Regards,

Nawaz Ahmed
Software Development Engineer

Fujitsu Australia Software Technology Pty Ltd
14 Rodborough Road, Frenchs Forest NSW 2086, Australia
T +61 2 9452 9027
Nawaz@fast.au.fujitsu.com
fastware.com.au




-----Original Message-----
From: Nicolas Karolak [mailto:nicolas.karolak@ubicast.eu]
Sent: Friday, 11 May 2018 5:04 PM
To: pgsql-admin@lists.postgresql.org
Subject: Re: Can I synchronize two master DB clusters except BDR ?

Hello,

While looking for a master/master replication solution i found this solution https://www.symmetricds.org/ but never
testedit, if you do i'm interested in a feedback.
 
I ended up using master/slave with automatic failover (with repmgr).

Cordialement,
Nicolas KAROLAK | SysAdmin
6-8, rue André Voguet - 94200 Ivry-sur-Seine
+33 1 77 56 77 96 | www.ubicast.eu | www.ubicast.tv


2018-05-10 15:37 GMT+02:00 JaeWon Lee <thejaewon@gmail.com>:
> Hi ^^
> I want to synchronize two master DB clusters. (Each generates its own
> DML
> statements)
> I'm using postgresql-10 server.
> I know BDR can synchronize two master DB clusters.
> But current BDR2 cannot synchronize postgresql-10 servers.
> As I know, upcoming BDR3 can synchronize postgresql-10 servers but I
> cannot afford to pay for it. ( $9,000 per server and I'm startup. )
> I'm considering two methods.
>
> (1) Retain postgresql-10 server and find some method  to synchronize
> two master DB clusters.
>  - I know logical replication cannot deal with my problem. ( it's one
> direction only )
>  - Is there other method to use ?
>
> (2) Downgrade my DB server to 9.4 and use BDR1 for synchronizing.
>  - As I know, I can use BDR1 for free now.
>  - I'm using basic functions of postgresql-10 so I think downgrading
> itself may not cause big  problem. But I'm worrying about unknown problem.
>  - Are 9.4 and 10 different significantly?
>  - Can I upgrade my 9.4 data to 10 later ? This is what I really worry
> about.
>
> Could you give me any idea ?
>

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Hi Lee,

>(1) Retain postgresql-10 server and find some method  to synchronize two
master DB clusters.
>- I know logical replication cannot deal with my problem. ( it's one
direction only )
> - Is there other method to use ? 
Unfortunately, no

>(2) Downgrade my DB server to 9.4 and use BDR1 for synchronizing.
> - As I know, I can use BDR1 for free now.
> - I'm using basic functions of postgresql-10 so I think downgrading itself
> may not cause big  problem. But >I'm worrying about unknown problem. 
> - Are 9.4 and 10 different significantly? 
Yes, Postgres 10 incorporated many a features in it.
> - Can I upgrade my 9.4 data to 10 later ? This is what I really worry
> about.
I think you could upgrade.

>Could you give me any idea ? 
One thing that strikes my mind is how you configure Logical Replication from
publisher to subscriber, same way you can do it for subscriber too. But
tried it, and it seemed to fail due to the replica_identity set or due to
primary key(orelse, we will end up with redundant data)
Refer the below link:

https://blog.dbi-services.com/can-i-have-the-same-table-published-and-subscribed-bi-directional-in-postgresql-10-logical-replication/

<https://blog.dbi-services.com/can-i-have-the-same-table-published-and-subscribed-bi-directional-in-postgresql-10-logical-replication/>

 

Regards,
Pavan



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